sql string querying with wildcard

[toonarific]

I currently have a php file that runs when users submit text in certain fields around my site. Right now, the file only looks for specifics words I enter into a table, and it only finds exact words. What I want to do is have the sql tring be able to use wildcard values around the {invalid_word} tag so it can find and prevent a user from submitting text if a long word contains the text on my banned list. Like, if I banned the word hair, and someone tried using the word hairball, it would let them. This is what the current php file code is


Code:

<?php
	# **** FIND BAD WORDS INTO THE ENTERED STRING **** #
	# @param $str - takes an argument as an string
	# match with database keywords
	# return true if bad word found
	# return false if bad word not found
	
	function findBadWords( $str ){
		
		$return = false;
		
		if( strlen( $str ) > 0 ) {
			$sql 		= "SELECT * FROM tbl_invalidunm WHERE MATCH (invalid_word) AGAINST (LCASE('".$str."') IN BOOLEAN MODE)";
			$rs 		= mysql_query( $sql ) or die( "Invalid query - ". mysql_error() );
			
			if($rs){
				$row_count 	= mysql_num_rows($rs);
				
				if( $row_count > 0 ) {
					$return = true;
				}
			} // if
		} // if
		return $return;
		
	} // end function 

?>